The effects of suspended sediment concentration on turbulence in an annular flume

Cloutier, Danielle; Lecouturier, Magali; Amos, Carl L.; Hill, Philip R.

doi:10.1007/s10452-005-4810-2

Cited by 21 publications

(13 citation statements)

References 42 publications

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“…1. This modification of the flow turbulent structure is attributed to the development of sediment induced vertical density stratification, which becomes more apparent at high concentrations (Cloutier et al, 2006;Sahin et al, 2013;Sahin, 2014). Presence of high concentrations of cohesive particles lead to plastic-like behavior, with significant increase in apparent bulk viscosity (Leeder, 1999).…”

Section: Resultsmentioning

confidence: 99%

Floc size variability under strong turbulence: Observations and artificial neural network modeling

Şahin

Güner

Öztürk

et al. 2017

Applied Ocean Research

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The flocculation of cohesive sediment in the presence of waves is investigated using high-resolution field observations and a newly-developed flocculation model based on artificial neural networks. Vertical profiles of suspended sediment concentration and turbulent intensity are estimated using measurements of current profile and acoustic backscatter. The vertical distribution of floc size is estimated using an artificial neural network (ANN) that is trained and validated using floc size measurements at one vertical level. Data analysis suggests a linear correlation between suspended sediment concentration and turbulence intensity. Observations and numerical simulations show that floc size is inversely related to sediment concentration, turbulence intensity and water temperature. The numerical results indicate that floc growth is supported by low concentration and low turbulence. In the vertical direction, mean size of flocs decreases toward the bottom, suggesting floc breakage due to increasing turbulence intensity toward the bed. A significant decrease in turbulent shear could occur within the bottom few-cm, related to increased damping of turbulence by sediment induced density stratification. The results of the numerical simulations presented here are consistent with the concept of a cohesive sediment particle undergoing aggregation-fragmentation processes, and suggest that the ANN can be a precise tool to study flocculation processes.

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Section: Resultsmentioning

confidence: 99%

Floc size variability under strong turbulence: Observations and artificial neural network modeling

Şahin

Güner

Öztürk

et al. 2017

Applied Ocean Research

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“…In laboratory experiments of kaolinite‐laden flow over a smooth, flat boundary, Baas & Best (2002) found that turbulence intensity increased near the base of flows with transient turbulent behaviour that possessed clay concentrations between 2% and 4% (see also Wang & Larsen, 1994; Wang & Plate, 1996; Wang et al. , 1998; Cloutier et al. , 2006).…”

Section: Discussionmentioning

confidence: 99%

The dynamics of turbulent, transitional and laminar clay‐laden flow over a fixed current ripple

Baas

Best

2007

Sedimentology

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Most aqueous sedimentary environments contain varying concentrations of fine-grained, often clay-rich, sediment that is transported in suspension and may modify the properties of the flow and underlying mobile bed. This paper presents results from a series of laboratory experiments examining the mean and turbulent properties of clay-laden (kaolinite) flows, of various volumetric sediment concentrations between 0AE046% and 12AE7%, moving over a fixed, idealized current ripple. As the kaolinite concentration was raised, with flow velocity and depth constant, four flow types were observed to occur: (i) turbulent flow, in which flow separation is dominant in the leeside of the ripple; (ii) turbulence-enhanced transitional flow, in which turbulence in the leeside separation zone region is enhanced; (iii) turbulence-attenuated transitional flow, in which turbulence along the separation zone shear layer and in the free flow above it becomes damped, eventually leading to a reduction in the size of the separation zone wake region; and (iv) laminar plug flow, in which turbulence is damped and flow is almost stagnant in the lee of the ripple. Such modulation of turbulence by increasing clay concentrations suggests that many paradigms of flow and bedform dynamics, which have been based on extensive past work in clear water flows, require revision. The present results highlight a need to fully characterize the boundary conditions for turbulence modulation as a function of clay type and applied flow conditions, and the effects of such flows on fully mobile cohesionless beds.

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“…The flow properties in Lab Carousel have been extensively studied (Thompson et al ., , , ), and the flume has been used in multiple sediment mobility studies (e.g. Cloutier et al ., , ; Lefebvre et al ., ).…”

Section: Methodsmentioning

confidence: 99%

Physical behaviour of Cretaceous calcareous nannofossil ooze: Insight from flume studies of disaggregated chalk

et al. 2016

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Geomorphic features such as drifts, sediment waves, and channels have been documented in the UpperCretaceous of NW Europe. These features are interpreted to result from bottom currents and have been used to refine chalk depositional models and quantify paleocirculation patterns. Chalk was first deposited as calcareous nannofossil ooze and geomorphic features are the result of sediment reworking after deposition.There is limited knowledge on the processes that govern nannofossil ooze mobility, thus forcing uncertainty onto numerical models based on sedimentological observations. This paper provides an extensive view of the erosional and depositional behaviour of calcareous nannofossil ooze based on experimental work using annular flumes. A fundamental observation of this study is the significant decrease of nannofossil ooze mobility with decreasing bed porosity. Erosion characteristics, labelled as erosion types, vary with total bed porosity (φ) and applied shear stress (τ 0 ). High-porosity ooze (φ > 80%) is characterized by constant erosion rates (E m ). At φ < 77%, however, erosion characteristics showed greater variance. Surface erosion was typically followed by transitional erosion (with asymptotically decreasing E m ), and stages of erosion with constant, and exponential E m . The estimated erosion thresholds (τ c ) vary from ~0.05-0.08 Pa for the onset of surface erosion and up to ~0.19 Pa for the onset of constant erosion (φ of 60-85%). Variability of deposition thresholds (τ cd ) from ~0.04-0.13 Pa reflects the influence of variable suspended sediment concentration (SSC) and τ 0 on settling particle size due to the identified potential for chalk ooze aggregation and flocculation. Additionally, τ cd seem to be affected by the size of eroded aggregates whose size correlates with bed porosity. Lastly, slow sediment transport without resuspension occurred in high-porosity ooze as surface creep, forming low relief sedimentary features resembling ripples. This process represents a previously undescribed mode of fine-grained nannofossil ooze transport.

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The effects of suspended sediment concentration on turbulence in an annular flume

Cited by 21 publications

References 42 publications

Floc size variability under strong turbulence: Observations and artificial neural network modeling

Floc size variability under strong turbulence: Observations and artificial neural network modeling

The dynamics of turbulent, transitional and laminar clay‐laden flow over a fixed current ripple

Physical behaviour of Cretaceous calcareous nannofossil ooze: Insight from flume studies of disaggregated chalk

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